Removal of sediment in silt and settling ponds is one of the more troublesome operations encountered in the coal industry and other industries requiring the use of such ponds. Silt ponds are customarily used in surface mining operations to trap silt entrained or suspended in run-off water flowing down from elevated surface mining sites. Settling ponds, on the other hand, are typically used to trap the effluent from coal washers and preparation plants which operate to extract the impurities in surface-mined and underground-mined coal.
In a surface mining operation, the silt ponds are usually formed by constructing an earth dam or some other kind of dam at an elevation appreciably below the mining site on a mountain or hill. Such silt ponds normally retain the run-off water long enough to permit the silt in the water to settle out to the bottom of the pond before the water is discharged from the pond, thereby allowing cleaner water to discharge through a trickle tube, riser pipe or spillway. Eventually, these ponds become so full of silt that they can no longer retain the water for a sufficient amount of time to allow for the efficient separation of the silt from the water. They therefore require continual cleaning. A similar situation arises with settling ponds.
After the silt is removed from a silt pond in a cleaning operation it must then be disposed of properly, and the ideal disposal site for the removed silt is up the mountain at the surface mining site where the silt originated. Such mining site is usually located at or near the top of the mountain in the form of a strip pit.
At the present time, the customary method of removing and disposing of the silt is to scoop or bucket the silt out of the pond with a dragline bucket, clamshell or backhoe and to place the removed material in a truck which is used to haul the silt from the pond site to the disposal site. Apart from being time-consuming and inefficient, this method of removing and disposing of the silt is costly and gives rise to a number of significant problems.
First, such a bucketing and hauling operation requires the construction of roads to bring in the heavy equipment to be used for cleaning out the pond and, more significantly, to truck out the silt from the pond to the disposal site. The road for hauling the removed silt up the side of the mountain to the mining site is difficult and costly to build, is usually in need of continual repair and quite often is extremely hazardous particularly when the road becomes icy or snow-covered during winter. Furthermore, its construction causes considerable disturbance to the soil and terrain.
Aside from the foregoing, bucketing the silt out of the pond has its significant shortcomings. To begin with, such a removal operation agitates or disturbs the pond, causing a considerable amount of the settled silt to again become suspended or entrained in the water. Furthermore, a considerable amount of the bucketed silt slips through the bucket as it is lifted out of the pond and thus spills back into the pond. Still further, the customary equipment used for removal of the silt is not specifically designed to reach all areas of medium and large sized ponds. Finally, one or more trucks must be on hand to receive the removed silt. In all, a crew of workers and several pieces of equipment are needed to provide for the removal and proper disposal of the silt.
While the foregoing problems plagued the coal industry, there have been numerous proposals spanning many years in the dredging and similar material moving arts. Representative teachings of such proposals appear in U.S. Pat. No. 2,438,637 issued on Mar. 30, 1948 to H. D. Jansen for Combined Conveyor and Excavator, U.S. Pat. No. 2,950,548 issued on Aug. 30, 1960 to K. Ritscher for Ditch Cleaning Machine, U.S. Pat. No. 2,968,879 issued on Jan. 24, 1961 to E. J. Rusich for Mechanical Harvesting Device For Cultivated or Reef Oysters, U.S. Pat. No. 3,470,633 issued on Oct. 7, 1969 to R. M. Soehnlen for Amphibious Dredge, U.S. Pat. No. 3,521,387 issued on July 21, 1970 to N. V. Degelman for Dredging Machine, U.S. Pat. No. 3,148,464 issued on Sept. 15, 1964 to K. M. Jones for Dredging Apparatus, U.S. Pat. No. 3,030,080 issued on Apr. 17, 1962 to M. L. Hise et al. for Apparatus For Removing Discrete Solid Material From A Pit, U.S. Pat. No. 3,050,289 issued on Aug. 21, 1962 to R. V. Gerner for Heavy Hydrocarbon Recovery, etc., U.S. Pat. No 4,052,311 issued on Oct. 4, 1977 to W. F. Martin for Apparatus For Separating Solids From Liquids, U.S. Pat. No. 3,852,384 issued on Dec. 3, 1974 to J. E. Bearden for Liquid Treatment Apparatus, and U.S. Pat. No. 3,865,727 issued on Feb. 11, 1975 to F. W. Broling et al. for Pumping Apparatus With Separating Mechanism.
The foregoing prior proposals are either unsatisfactory or disadvantageous for use in removing and disposing of settled sediment in a silt or settling pond. For example, dredging equipment using suction pumps or the like requires a high water-to-solids ratio and thus withdraws considerable water in the course of removing the solid material. Aside from being inefficient, such a method of removal is unsatisfactory where, as in silt and settling ponds, the amount of water in the pond is relatively small and must be retained in the pond if the settling process is not to be interrupted or degraded by lack of sufficient water. Furthermore, such a suction type dredging technique, like other types of dredging operations using buckets, stirs up and unsettles a large amount of sediment, causing it to again become entrained in the water. Thus, despite the presence of such prior art proposals over the years the coal industry nevertheless has continued to use the problem-plagued bucketing and hauling technique described above for removing and disposing of the silt or other sedimentary matter.
In comparison with the foregoing state of the art, the present invention is capable of more efficiently and more economically removing the sediment from the bottom of the pond without removing any substantial quantity of the water (i.e., the water above the bed) and without disturbing the settled sediment in the bottom of the pond. Moreover, the system embodying the principles of the invention does not required the construction of costly haul roads.